This invention relates to inspection systems and, more particularly, to an apparatus for examining hardware items to determine their characteristics.
The manufacture of small hardware items, such as nuts and bolts, is a largely mechanized highspeed operation. The manufacturing cost of individual units of the finished product may typically be a fraction of a cent, so a careful manual or visual inspection of individual units is generally impractical. Accordingly, such inspection is normally omitted and a disturbing percentage of defective items can appear in any given batch.
In certain instances the presence of even a small number of defective hardware items can have severe consequences. An example is the manufacture of fasteners known as "Teenut" fasteners. The fastener nuts have a small integral body which consists of a cylindrical neck portion and an annular flange which extends radially at one end of the neck. The neck portion has an inner threading which is formed by a stamping operation during manufacture. Unfortunately, the stamping operation is not perfect and some nuts pass through production without receiving an inner threading. The completed fastener nuts are utilized for fastening together larger metal parts, e.g. the body metal of an automobile. If, after a number of nuts have been welded to a body member, it is discovered that one nut is without threading, the whole member can be considered a reject. Worse yet, an improper and incomplete fastening of body members can result from such an occurrence. In view of this possibility, Teenut fasteners are ordinarily inspected visually by workers to segregate non-threaded nuts as a final stage of nut manufacture. This operation insures against the presence of most defects but is subject to human error and involves labor expense.
In the U.S. Pat. No. 3,816,746, assigned to the same assignee as the present invention, there is disclosed an apparatus for automatically examining the surfaces of hardware items progressing along a track toward a first receiving location and for urging the items toward a second receiving location when a specified surface condition is detected; viz., the absence of threading. Briefly, a laser beam is directed toward the supposedly threaded surface and scanned thereon transverse the direction of the threads. A photodetector is disposed to detect light reflected from the surface. Since a threaded surface has different reflection properties than a non-threaded surface, the photodetector output can be utilized to detect non-threaded items and these are automatically deflected toward the second receiving location.
The apparatus described in the above-referenced patent operates quite satisfactorily, but there are other characteristics of hardware items which it would be desirable to automatically inspect without the need for employing unduly expensive additional equipment or complex modifications to present equipment. For example, when nuts are initially fed to a tapping machine, it is found that some of the nut "blanks" do not have the desired hole in the center, this commonly occuring due to defects in the molding procedure. When a nut blank with a blocked hole is fed to the tapping machine, the tap can be damaged which results in expensive tap repair and down time. Accordingly, visual inspection, which is subject to human error and involves labor expense, is sometimes used. It would be desirable to have a machine which could automatically and reliably perform this function. It would also be desirable to have the ability to sort hardware items in accordance with their thread coarseness or their height dimensions, these functions also being commonly performed by visual inspection. It is, in particular, an object of the present invention to provide a single versatile machine which has the capability of performing automatic inspection techniques of various characteristics of hardware items with a minimum of optical and electronic components which serve multiple purposes as desired by a user.